1. Field of the Invention
The present invention relates to gaming machines in which racing, such as horse racing, bicycle racing, boat racing, and dog racing, is modeled and bettors predict the order of finish of objects, such as model horses running on tracks in a race, and bet on the race. A dividend is paid to the bettors who have correctly predicted the winner, the dividend being the product of a bet amount and odds on the winner. The objects are not limited to models, and they include images displayed on a display monitor.
2. Description of the Related Art
Conventional gaming machines in which horse racing or dog racing is modeled and races are simulated have been known. In such conventional gaming machines, running objects, such as model horses by way of example, run on oval tracks, and bettors predict the winner of a particular race and bets on the race before the start of the race. As in actual horse racing or the like, the bettors can select from various bet types, such as straight, “single frame” (Japanese system of wagering in which a bettor places a bet on a frame that consists of two horses and the bettor wins the bet if one of the horses finishes first in a race), exacta, and quinella betting. In these bet types, odds (dividend rate) are displayed in accordance with each horse, each frame, or each combination thereof. Each of the bettors selects an object to place a bet on by taking into consideration risks and returns.
The betting is closed before the start of the race. The race is actually held using the running objects. A dividend is computed by multiplying a bet amount by odds for each bet, and dividends on all the bet objects are summed. The bettors who have correctly predicted the winner receive payouts.
Unlike actual horse racing or the like, in conventional gaming machines, generally a computer controls running of the running objects and sets the order of finish by drawing lots using random numbers in accordance with a predetermined strength (probability of winning) of each running object. In other words, the probability of winning of each running object is preset, and a first place finisher among all the running objects is determined in accordance with the preset probabilities of winning. A second place finisher is determined among the remaining running objects. Similarly, the order is determined until the last place finisher is determined. Therefore, the order of finish has already been set in the gaming machine prior to the start of the race or within a predetermined period of time from the start of the race. Simulated races using running objects are intended to make bettors feel the atmosphere of races and to inform the bettors of the order of finish in a particular race.
For the owner of a gaming machine, profits are the difference obtained by subtracting the total payouts from the total bet amounts placed by bettors. In order to ensure that the owner receives stable profits, the owner configures a target payout rate in advance. The probability of occurrence of each race result (such as the probability of a certain horse winning in a race) and odds set relative to the probability of winning are determined so as to statistically achieve the target payout rate. In straight betting, the probability of winning of each horse is set for each race. The quotient of the target payout rate divided by the preset probability of winning of each horse indicates the odds to be set on each horse in order to achieve the target payout rate. Table 1 shows an example of setting of the probabilities of winning and the odds.
TABLE 1No. 1No. 2No. 3No. 4No. 5No. 6Prob. of winning (%)5.841.0173.442.6115.491.61Odds15.4189.111.22534.485.8155.90
Table 1 indicates the probabilities of winning and the odds on horses in so-called straight betting. The first row of Table 1 indicates numbers assigned to horses. The second row indicates the probability of winning (percentage) set for each horse. The third row indicates odds set for each horse. The odds are computed so as to achieve a target payout rate of 90%.
In the description hereinafter, the probability of winning and the odds set for each horse are simply referred to as the probability of winning of each horse and the odds on each horse.
As shown in Table 1, the quotient may not be an integer depending on a combination of the target payout rate and the probability of winning. The quotient may happen to be indivisible within an appropriate number of digits. In the following description and tables, an indivisible decimal is rounded to an appropriate numeral. Actual computation is performed with an appropriate number of significant digits.
In the example shown in Table 1, when actual payouts are taken into consideration, odds which are not integers are required to be rounded to an appropriate digit. Specifically, the product of the bet amount and the odds is the payout amount. When odds with numerous decimal places are used, it is cumbersome to deliver payout amounts less than the minimum payout unit.
For example, when the minimum payout unit is a coin, it is impossible to deliver the fractional part of the payout. In general, non-integer odds are rounded up, rounded down, or rounded off so that the odds become an integer or have one decimal place. The rounded odds are then indicated to bettors.
Table 2 shows an example of rounded odds.
TABLE 2No. 1No. 2No. 3No. 4No. 5No. 6Prob. of winning (%)5.841.0173.442.6115.491.61Odds15.4189.111.22534.485.8155.90Rounded odds1690235656Payout rate (%)93.4490.9146.991.3592.9490.16
When the odds are rounded, another problem occurs in that the payout rate is also changed by rounding the odds.
The fourth row of Table 2 indicates the payout rate (the expected payout rate for bettors) for each horse determined by the odds shown in Table 1.
The payout rate for each horse is computed by (probability of winning of each horse)×(odds).
In Table 2, the payout rate for horse No. 3 exceeds 100%. This means that when bets are continuously placed on horse No. 3, statistically, payouts larger than the bet amounts will always be delivered.
Although the probability of winning of each horse is an internal numeral and hence it is not easily predictable by bettors, prediction to a certain extent can be performed by statistically examining the results of many races. Since the odds are disclosed, it is possible to predict the payout rate. Therefore, when a bettor recognizes that there is a horse with a payout rate of more than 100%, the bettor will certainly place a bet on that horse.
Such settings are not favorable for the owner of a gaming machine. Depending on the country, such settings may infringe on laws concerning gaming machines.
It is possible to match the payout rate of each horse to the target payout rate by adjusting the probability of winning using rounded odds. Since the sum of the probabilities of winning must equal one, inaccurate adjustment will fail to correct the payout rates.